Control for clothes dryer



1366- 1958 E. L. ZEHRBACH CONTROL FOR CLOTHES DRYER Filed May 23, 1956 FIG.|.

INV ENTOR EDGAR L. ZEHRBACH BY ATTORNEY HEN CONTROL FUR (CLOTHES DRYER Edgar Zehrhach, Mansfield, Ohio, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pan, a corporation of Pennsylvania Applicationltllay 23, 1956, Serial No. 586,852 it claims. bi. Fi l- 15) This invention relates to a dryer for fabrics and has for an object to provide an improved, simplified control mechanism for a dryer of this kind.

A further object of the inventionis to provide an tumbling the fabrics and circulating air thereover anda heater for said air energizable at low and high rates. Preferably, the heater is energized selectively from high and low voltage sources such as an Edison three-wire, single phase circuit. Accordingly, when drying fabrics capable of being (tried at relatively high temperature, the heater may be energized at the higher voltage and, when fabrics which must be dried at relativel.y low temperature are being treated, the heater is energized at'lower voltage.

The control includes switching means for-energizing and deenergizing the motor driven means and a pair of switches respectively connected to the high and low voltage electrical sources for controlling energization of the heater. The switching means and said switches are actuated by a cam driven by a conventional timing motor, thelatter being preferably under control of the switching means for the motor driven means. The cam is manually movable from an inactive station, in which the switching means and said pair of heater switches are open, into first and second selective, activeranges of movement. ln the first range, one of the switches is closed for energizing the heater from the higher voltage sourceand, in the second range, the other switch is closed for energizing the heater from the fewer voltage source. The switching means is closedinhoth ranges so that the motor driven means-is energizedfor turnhlingthefabricsand circulation of air.- Since the timer motor is controlled by the switching'means,

it is operated to drive the camthrough the range of novement into which it has been adjusted,r to the inactive stationofthe'cam, where the switching meansand the pair of heater switches are opened. The period of time that the timer operates depends upon the amount the is manually moved into the active range ofmovement-thereof. k

These and other objects are effected by theinvention as will be apparent from the following description and claims-taken in connection with the accompanyingdraw ings, forming a part of this application, inwhich-z Fig. 1 is a transverse sectional view taken through one fornroi dryer controlled in accordance withthe inventionyand' t n Fig, 2 is a diagram of the" electrical connections -befween the electrical 't ransla'tihgdei icesdf the" dryer and p assazzt Patented Dec. 9, 1958 therefrom. A generally cylindrical basket 15 is arranged within the drying chamber 12 and mounted for rotation about a horizontal axis. it will be understood that the cylindrical side wall of the basket is perforate substantially throughout its extent for the passage of air translated from the air inlet duct 33 through the basket 15 to the discharge duct 14. The basket 15 is, preferably, provided with a plurality of radially inwardly extending vanes 16 for tumbling the fabrics during the drying operation. The casing 10 and basket 15 have conventional registering openings (not shown) formed therein for providing'access to the interior of the basket 15.

The basket is suitably journaled in the casing ill for rotation about a horizontal axis and is driven by a sheave 17 belted, as shown at 18, to an electric motor 19 sup ported by the bottom of the casing 10. The motor 19 also functions to drive a blower runner 21 arranged within a blower housing 22. The latter is provided with an air inlet opening 23 communicating with-the space within the casing 10, which space receives air from the surrounding atmosphere through openings 2&- formed. in the casing side wall. The blowerv housing 22 discharges into a generally horizontal duct 25 within which an electric heater 26 of suitable construction is disposed for heating the air discharged by the blower runner 21. The heated air passes through the duct 13 to the drying chamber 12 and thence to the interior of the basket 15 for contactingthe tumbling fabrics and the vaporization of Water therein. The vitiated air and the water vapor absorbed hereby pass to thedischarge duct 14.

In the operation of the dryer as set forth above, the heater is energized at' a relatively high rate when drying fabrics which are capable of being dried at relatively high temperatures. Conversely, when treating synthetic fabrics and others which must be dried at relatively low temperature, the heater is energized at a low rate. The high andlow rates of energization of the heater are elfected by connecting the heater to high and low voltage electrical sources. Preferably, the heater is connectible to multiple voltages of an Edison three-wire, single-phase circuit in order to provide the high and low rates of energization; The duration of the drying period is also variablein order to vary the amount of water remaining in the fabrics after treatment. operation is carried out by a timer constructed and arranged in accordance with the invention and having provision for controlling the rate of energization of the heaters. The timer, therefore, may, upon a single manual adjustment thereof, control the duration of the drying period and the rateof energization of the heating means. The controland timer for'the dryer will now be described.

The source of energy for the motorlfi and the heater 26 is represented by a three-wire, single-phase circuit having main conductors L and L and a neutral conductor N (Fig. 2). It is understood that the potential between either main conductors L or L and the neutral is volts and the potential across conductors L and L is 230 volts. The motor 19 is disclosed as a split phase motor having arunning winding 28 and a starting windra es; the latter being controlled by a conventional This 3 centrifugal switch 31. As is understood, switch 31 is closed at all times that the motor speed is below a predetermined value.

The timer which is constructed in accordance with the invention is generally shown at 32 and includes a motor 33 of the type commonly used in clocks. The motor 33 drives a cam shaft 34 at a low speed of, for example, one revolution in four (4) hours. Usually, a reduction gear mechanism (not shown) is interposed between the motor 33 and shaft 34. The shaft 34 carries a cam. 35 for operating switches, referred to later, and a knob 36 by which the timer 32 may be manually set to carry out variable periods of operation and different rates of energization of the heater 26. As shown, the knob 36 is movable to two inactive or off positions, wherein the dryer is entirely deenergized.

The cam 35 actuates a pair of switch structures, one of which includes resiliently supported contacts 37, 38 and 39 and the other of which includes the resiliently sup ported contacts 41 and 42. The recited contacts are carr'i'ed by respective leaf springs, as is well understood, and the contact 37 is actuated by a cam follower 43 riding upon the cam 35. The contact 41 is actuated by a follower 44 also riding upon the cam. The cam is provided with a pair of depressed portions 45 and 46 in which the followers 43 and 44 rest in the off or inactive positions of the cam. The cam includes a lobe 47 of maximum radial height and a pair of lobes 48 and 49 of lesser radial height. The arrangement is such that, when the follower 43 rides upon the lobe 47, the contact 37 is forced into engagement with contact 38, and the latter is forced into engagement with contact 39. Accordingly, contacts 37, 38 and 39 are electrically connected. When the follower 43 engages lobes 455 or 49, the contacts 37 and 38 are engaged, while contacts 38 and 39 are disengaged. The contacts 41 and 42 areengaged only when the follower 44 rides upon the lobe 47 and are disengaged at other times.

The timer knob 36 may be provided with indicia cooperating with a fixed mark or pointer 51. The indicia is divided into first and second groups indicated at A and B, respectively, with intervening off or inactive positions. The indicia 10 to 68, inclusive, in group A indicate minutes of operation, and the index Dry is employed when complete drying of the fabrics for immediate storage is desired. The indicia 10 to 100, inclusive, in the range B indicate minutes of dryer operation. As set forth hereinafter, fast drying at maximum heat is carried out in the range A while slower drying at reduced heat is effected with the timer set in its range B. Preferably, the ranges A and B of the knob 36 are provided, respectively, with designations High and Low which, when read with pointer 51, indicate the rate of heating and drying being carried out.

As shown in Fig. 2, the line conductor L is directly connected to contact 38 and the contact 39 is directly connected to one terminal of the heater 26. The other terminal of heater 26 is connected to line conductor L through the contacts of a relay 53 having an operating coil 54. The neutral conductor N is connected directly to contact 41 and the contact 42 is connected by a conductor 55 to the heater 26. 'As set forth more in detail hereinafter, the contacts 38 and 39 are closed, with the timer adjusted into its active range A, so that the heater 26 is energized at maximum voltage for maximum heat. When the timer is adjusted into its active range B, the contacts 41 and 42 are engaged and contacts 38 and 39 are disengaged so that the heater is connected to line conductor L and the neutral'N. Accordingly, the heater is energized at lower voltage for reduced heat. The conductor 55 is shown connected to an intermediate portion of the, heater 26, although it may connect with the terminal thereof which is connected to contact 39. The point of the heater 26 to which the conductor 55 is connected 4. determines the wattage of the heater when energized at the low voltage, all of which is well understood.

In order to prevent overheating of the fabrics when complete or bone drying is carried out, a thermostat 56 having fixed contacts 57 and 57a and a bridging contact 58 is employed. This thermostat 56 is manually closed or opened in any suitable manner as by a handle 59 diagrammatically shown in Fig. 1. It will be further understood that the thermostat 56 is thermostatically opened in response to a temperature within the drying chamber 12 obtaining when the clothes are completely dry. The thermostat 56 does not close automatically upon drop in temperature but must be manually closed. Since thermostats of this kind are well understood in the art, further description of the thermostat 56 is deemed unnecessary. It is set forth, however, that this thermostat 56 is arranged to reflect the temperature of a portion of the drying chamber that closely follows the temperature of the fabrics being treated.

As shown, one fixed contact 57 of the thermostat 56 is directly connected to the contact 37, while the other fixed contact 57a is connected to one terminal of relay coil 54. The opposite terminal of the relay coil 54 is connected to a terminal of the starting winding 29 of the motor 19. It will be apparent that, when the contacts 37 and 38 are engaged and the contacts 57 and 57a of thermostat 56 are bridged by member 58, the relay coil is energized in series with the motor starting winding 29 across line conductor L and neutral N. From this de scription, it will be seen that when the centrifugal starting switch 31 of the motor 19 is closed because of an abnormally low speed or stoppage of the motor 19, the coil 54 is shunted by the switch 31 through a conductor 61, bridge 58 and the contact 57a, so that the relay 53 opens, deenergizing the main heater 26. Since the motor windings 28 and 29 are energized through the bridge 58 of thermostat 56 and conductor 61, the motor 19 is controlled by the thermostat 56, except as noted hereinafter.

In order to assure continued operation of motor 19 and the circulation of cooling air after the heater 26 is deenergized by opening of thermostat 56, another thermo stat 62 is employed for the control of motor 19. This. thermostat 62 is subjected to the heated air and is preferably arranged in the duct 13 on the downstream side of the heater 26. The thermostat closes at a temperature of, for example, 150 F. and opens at a lower temperature of, for example, F. The thermostat 62 is connected in shunt with the contact 57 and bridge 58 of thermostat 56, so that continued operation of the motor 19 and circulation of cool air are carried out for a period of time after the thermostat 56 opens or until the thermo stat 62 is cooled to its opening temperature. The use of a thermostat of the type shown at 62 is old in the art and need not further be described.

In operating the dryer for the drying of a full load of fabrics which may be dried at relatively high temperature, the timer knob is rotated into the active range A after the load of damp fabrics is deposited in the basket. If complete drying is required, the knob is actuated to the Dry setting and the thermostat 56 is manually actuated by the button or handle 59 to engage bridge 58 with the contacts 57 and 57a. As described, the contacts 37, 38 and 39 are electrically connected as the follower 43 now rides on lobe 47. Contacts 41 and 42 remain disengaged, as described, because follower 44 now rides on lobe 49. Accordingly, the main motor windings 28 and 29 are energized by a circuit including line L contacts 38 and 37, contact 57, bridge 58, conductor 61, windings 28 and 29 and neutral N. The relay coil 54 is energized in series with starting winding 29 as soon as the motor starting switch is opened during acceleration of the motor as described heretofore. Accordingly, the motor 19 operates to tumble the fabrics in the rotating drum 15 and to drive the blower for the translation of air to the dryses,

ing chamber 12. The air is heated by the heater 26 which is now energized at high rate by line conductors L and L it being under that contacts 38 and 39 are engaged and relay 53 is closed.

As the circulated air becomes hotter, the temperature of the thermostat 62 increases to its closing value, so that this thermostat closes the shunt circuit across contact 5'7 and bridge 58. This is of no moment at present, as contact 57 and bridge 58 are engaged, as described. At this time, the major portion of the energy dissipated by the heater is converted to latent heat of vaporization in the drying chamber 12 because of the copious quantity of water in the fabrics. Accordingly, the temperature in the chamber 12 is relatively low. As the fabrics become dried, the temperature in the chamber increases as more of the energy dissipated by the heater is converted to sensible heat and less to latent heat. When the fabrics are completely dry, the temperature in chamber 12 will have increased to the value at which thermostat 56 disengages the bridge 58 from contacts 57 and 57a. The disengagement of bridge 53 and contact 5711 deenergizes relay 53 so that the heater Z6 is deenergized.

Circulation of cool air continues because the motor is energized by the shunt circuit provided by thermostat 62 and connecting the disengaged contact 57 and bridge 58. The circulation of cool air continues until thermostat 62 is reduced in temperature to its opening value of about 130 F. At this time, the circuit to the motor 19 is opened and the latter stops. The timer motor 33, being connected directly in parallel with main motor 19, operates only at such times that the main motor operates. Accordingly, the cam 35 is slowly advanced, clockwise, during the drying operation just described, and is stopped upon deenergization of the timer motor. This is usually prior to the returning of the timer cam and knob to the off position.

If, instead of complete drying, only partial drying of the fabrics is desired, the knob will be advanced to the appropriate time index in range A which the operator knows by experience is proper for the particular load being treated. With this drying program, the timer is driven to its off position before the thermostat 56 is heated to its opening temperature. Accordingly, the heater 21s is deenergized when the contacts 38-39 open, which operation is effected when the follower 43 rides off the lobe 5'7 upon the lobe 48. After about 8 to 10 minutes of circulation of cooling air, the motor 19 is deenergized by the disengagement of contacts 37 and 38, which operation is effected when the follower 43 rides off lobe 43 into the depression 46. The amount of water left in the fabrics may be varied by properly positioning the timer knob. The further the knob is advanced, the shorter the period of operation, as indicated by the time indicia, and the greater the amount of water remaining in the fabrics.

The drying of fabrics at relatively low temperature is carried out by adjusting the knob 36 into its active range B. The position to which the knob is adjusted will be known to the operator by experience. Some fabrics require greater periods for drying than others and the weight of the load must also be given consideration by the operator. In drying at reduced temperature and wattage, the period of operation is usually that determined by the operator, because the heat generated is usually insufficient to raise the temperature in the chamber 12 to the value at which the thermostat 56 disengages the bridge 53 from contacts 57 and 57a. Accordingly, the cycle is terminated in most instances by the timer returning to the off position and not by the opening of thermostat 56 in response to temperature.

When the timer is positioned in its range B for low temperature drying, the follower 43 rides on lobe 49 so that contacts 37 and 38 are engaged for energization of the main motor 19, timer motor 33 and relay coil .ggtg.

g 54 as described. Gontacts The follower 44 now rides on lobe 47 so that contacts 41 and 42 are engaged. With relay 53 closed, as described, the heater 26 is energized by main conductor L and neutral N at relatively low voltage. The wattage of the heater at this time will depend upon the resistance of the portion of the heater that is active, as is well understood.

During the drying of the fabrics, the timer cam advances clockwise and, at the end of the preselected period, the follower 44 first rides off lobe 47 upon lobe 48 so that contacts 41 and 42 separate for deenergizing the heater 26. As described, the motor 19 and timer motor 33 continue to operate, the former effecting operation of the blower for the circulation of cooling air through the basket 15. Operation of both motors is terminated when the follower 43 rides off lobe 49 into the depression 45 thereby disengaging contacts 37-38. During this low temperature drying cycle, the thermostat 62 may close and subsequently open but this is of no moment because, as set forth, the thermostat 56 usually remains closedduring this cycle. However, it is pointed out that, if the thermostat 56 did open during a low temperature drying cycle, the cycle of operation would terminate in exactly the same manner as described in connection with the high temperature drying cycle.

From the foregoing description, it will be apparent that an improved control for a dryer is provided wherein, by a single adjustment, the duration of the drying cycle and the rate of energization of the heater are selected. Accordingly, the operator may readily select the amount of water remaining in the load at the conclusion of the cycle and the temperature of the air utilized for the drying operation.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What is claimed is:

1. In a dryer, the combination of means defining a drying chamber, means for translating air through said drying chamber, means for heating the air, a timing mechanism controlling operation of the air translating means and the air heating means, said timing mechanism being manually adjustable, selectively, from an inactive station wherein the air translating and air heating means are deenergized, into first and second active ranges of operation, said timing mechanism including, means for returning it to its inactive station at the conclusion of a period of active operation determined by the position in the active range to which the timing mechanism is adjusted, means responsive to adjustment of the timing mechanism into either of its active ranges of operation for actuating the air translating means, means responsive to adjustment of the timing mechanism into its first active range of operation for energizing the heating means at a relatively high rate and means sponsive to adjustment of the timing mechanism into its second active range of operation for energizing the heating means at relatively low rate.

2. In a dryer, the combination of means defining a drying chamber, means for translating air through said drying chamber, means for heating the air, sources of relatively high and low voltage electricity, a timing mechanism controlling operation of the air translating means and the air heating means, said timing mechanism being manually actuated, selectively, from an inactive station wherein the air translating and air heating means are deenergized, into first and second active ranges of operation, means returning the timing mechanism to its inactive station at the conclusion of a time period determined by the position to which it is adjusted in its ranges of operation, means responsive to adjustment of the timing mechanism from its inactive station into either of said ranges of operation for energizing the air translating means, means for energizing 38-39 are now disengaged:

7 the heating means by said high voltage electrical source in response to adjustment of the timing mechanism into its first active range of operation, and means for energizing the heating means by the low voltage electrical source in response to adjustment of the timing mechanism into its second active range of operation.

3. In a dryer, the combination of means defining a drying chamber, means for translating air through said drying chamber, means for heating the air, sources of relatively high and low voltage electricity, a timing mechanism including respective switching means controlling the heating means and the air translating means, means for manually actuating the timing mechanism selectively from an inactive station wherein said switching means is open into first and second ranges of movement, means for returning the timing mechanism to its inactive station at the conclusion of a period of time determined by the position to which the timing mechanism is adjusted in one of its ranges of movement, means closing the switching means for the energization of the air translating means in both ranges of movement of the timing mechanism, said switching means for the heating means being closed to connect the heating means to the relatively high voltage electrical source in one range of movement of thetiming mechanism and to the lower voltage source in the other range of movement of the timing mechanism.

4. In a clothes dryer, the combination of means defining a drying chamber, means for translating air through said chambenan electric heater for heating the air, a timing mechanism controlling energization'of the air translating means and said heater, and high and low voltage electrical sources, said timing 'mechanism including a driving motor, a cam rotated thereby, switching means actuated by the cam andcontrolling energization of the air translating means and said motor, first and second switches controlling energization of the heater and actuated by the cam, said first and second switches being connected, respectively, to said high voltage and low voltage electrical sources and means for manually rotating the cam from an inactive station wherein said switching means and said first and second switches are open into first and second active ranges of movement, said switching means being closed in both active ranges of movement of the cam, and said first and second switches being closed, respectively, in the first and second ranges of movement of the cam and open at other times.

References Cited in the file of this patent UNITED STATES PATENTS 2,550,118 Kauffman Apr. 24, 1951 2,621,423 Clark Dec. 16, 1952 2,707,837 Robinson et al May 10, 1955 2,778,914 Vallorani Jan. 22, 1957 

